* combine.c (make_extraction): Reapply to the argument of an ASHIFT.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@54846 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b7fb376..4a42c58 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2002-06-20  Richard Sandiford  <rsandifo@redhat.com>
+
+       * combine.c (make_extraction): Reapply to the argument of an ASHIFT.
+
 2002-06-20  Rainer Orth  <ro@TechFak.Uni-Bielefeld.DE>
 
        * config/sparc/t-crtfm (crtfastmath.o): Prefix with $(T) for

diff --git a/gcc/combine.c b/gcc/combine.c
index 3b29882..ea12b13 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -5968,6 +5968,21 @@ make_extraction (mode, inner, pos, pos_rtx, len,
        is_mode = GET_MODE (SUBREG_REG (inner));
       inner = SUBREG_REG (inner);
     }
+  else if (GET_CODE (inner) == ASHIFT
+          && GET_CODE (XEXP (inner, 1)) == CONST_INT
+          && pos_rtx == 0 && pos == 0
+          && len > INTVAL (XEXP (inner, 1)))
+    {
+      /* We're extracting the least significant bits of an rtx
+        (ashift X (const_int C)), where LEN > C.  Extract the
+        least significant (LEN - C) bits of X, giving an rtx
+        whose mode is MODE, then shift it left C times.  */
+      new = make_extraction (mode, XEXP (inner, 0),
+                            0, 0, len - INTVAL (XEXP (inner, 1)),
+                            unsignedp, in_dest, in_compare);
+      if (new != 0)
+       return gen_rtx_ASHIFT (mode, new, XEXP (inner, 1));
+    }
 
   inner_mode = GET_MODE (inner);